Process of bending wood



May 2, 1933.

Filed Nov. 3. 1950 2 Sheets-Sheet 1 H- s; I CESS 0F BENDIN May 12, '1933.

H. s. McLEOb 1,906,392

PROCESS OF BENDING WOOD Filed Nov. 3, 1930 2 Sheets-Sheet 2 flee/ .5 yqfay,

Patented May 2, 1933 UNITED STATES HARRY S. MCLEOD,

OF DELPI-IOS, OHIO PROCESS OF BENDING WOOD Application filed November It is the object of my invention to make bent-wood articles, especially thick articles, that will maintain their proper shape and dimensions aft-er being bent; and, incidentally,

at the same time to make such articles .of pieces that are thinner and therefore less costly.

There are many places where it would be advantageous to use bent-wood articles, but

where they have not been used in the past because of the apparently unavoidable tendency of such bent wood, especially in the thicker articles,-to change indeterminately in shape and dimension over a considerable period 1 after the bendinga period that may continue for weeks and months. For instance,

in certain automobile-body bows, made of wood an inch or more thick and having an intermediate portion that is relatively straight or nearly straight and end portions that are bent into approximate quarter-circles, a prohibitive change in dimension, sometimes in excess of an inch, occurs in the distance be-.

tween the two ends when these parts are made of single-piece bent wood. This change is an uncertain thing, for sometimes it is a lengthening and sometimes a shortening; and it has heretofore largely prevented the adoption and use of bent wood in man 80 places where otherwise it is well adapted for use.

Probably this uncertain change in shape and dimension has been theresult of heavy local stresses set up in the wood structure during the bending. As the bending is done, even of wood'carefully steamed, there is some stretching at and near the outer surface of the bend and a greater compressing and up-' setting at and towards the inner surface of 40 the bend. The degree of this stretching, and

of this compressing and upsetting, andtherefore the difi'erence between effects on the wood structure at and near the outer and inner surfaces respectively, increases with the thickness of the wood; so that while relatively small in thin veneers it becomes very large in thicker pieces, say of an inch thickness and upwards. i

It has been proposed to make these thicker '50 bent-wood articles of several plies, bent sep- 3 and one 3, 1930. Serial No. 492,926.

arately and then glued together. While this has helped some, by lessening to some extent the distortion foll wing bending, it has not I been of sufficient help to make bent wood generally available for constancy of dimension. g

' I have found, however, that it is possible to obtain much greater constancy of dimension inbent-wood articles, and a constancy that is well within commercial limits even in thick articles, by making such articles of a plurality of plies Which while softened by steaming arebent simultaneously and while in contact in the relative order the are to have in the finished article, so that each ply serves as a form for its neighbor or neighbors in the bending operation; then letting the bent group of plies dry and set while held together; and then gluing said plies together. The built-up article thus made may be worked and finished in the usual manner, just as if it were of one piece. For instance, an article that in the rough is to be an inch and a half thickmay be built up of three plies each a half-inch thick, or of two plies each three-quarters of an inch thick, or of four plies each three-eighths of an inchthick, or of one three-eighths-inch half-inch and one five-eighths-inch ply. v. The abutting surfaces of the adjacent plies slide on and conform to each other during the bending, and thus avoid the production of the heavy stresses that are produced in the wood structure when the same bending is done of a single piece equal in thickness to the combined thickness of the group of plies. The drying and setting of the plies'while they are kept in contact results in the avoidance of relative distortion between the plies which are to hem contact inv the finished article. The gluing together of the group of plies after they have dried and set holds them in the proper relative,- position, with 95 relatively little stress in the wood structure in comparison with that existing in a corresponding single-piece article, and with the stresses which do exist in the separate plies largely balancing each other because of the 1 parts requiring any real 65 resistance which the glued surfaces present against the relative slipping that any distortion would tend to produce.

In the accompanying drawings I have illustrated my invention in connection with the making of multi-ply automobile-bows. Figs. 1, 2 and 3 are front elevations of a group of plies of lumber that are to form a multi-ply automobile-bow, in initial position prior to bending, in partly bent position, and in completely bent positlon ready for drying, respectively, and show also the bending form and fragmentally some parts of the bending machine, which per se may be of any desired type; Fig. 4 is a perspective view of a plurality of such groups that were all bent simultaneously in the bending machine, held ready for drying in the form in which they were bent; Fig. 5 is a perspective view of the same plurality of groups, after they have dried and set sufiiciently to be removed from their bending and retaining form; Fig. 6 is a perspective view showing the several plies of a group that is to form one automobile-bow, separated for applying the glue; Fig. 7 is a plan showing the same three plies put back together again after the applying of the glue and held together on a gluing form while the glue sets; and Fig. 8 is a perspective view showing a multi-ply automobile bow, in the rough at one end and finished at the other.

The lumber of the proper thickness for the various plies is cut into the desired lengths, finished fiat as by planing on the surfaces which are to lie against other surfaces, assembled in groups with such flat surfaces together and in the order they are to have in the finished article and temporarily held together in said groups by one or more nails 10, which although shown driven home are not necessarily so and which are later removed, and given the usual steaming treatment which is commonly preliminary to bending. The assembly into groups may be either before or after the steaming, but is most conveniently before steaming. The difi'erment plies of a group are of suitably differ ent lengths graduated from the shortest length for the ply that is to be on the inner side to the greatest length for the ply that is to be on the outer side of the article after the bending. In the example shown, the article to be made is an automobile bow, and

' is made of three plies 11, 12, and 13 of 'successively greater length, so that the shortest ply 11 will eventually be on the inner side and the longest ply 13 will eventually be on the outer side.

After the lumber has been softened by the steaming, one or more of the assembled and steamed groups are put on a suitable form 15, (of which there are a number,) and bent into the desired shape in the usual bending machine. As bending machines are wellknown, I have show merely the fixed formfully bent, The forms 15 are of flexible sheet metal, such as sheet brass, usually of sufficient width to hold a number of bows, four as illustrated; and at their ends have rigid end-pieces 20 which have upturned end flanges 21 between which the plies of lumber lie. As the bending is done, by the simultaneous pulling of the two chains 18 and the resultant simultaneous tilting of the two bending levers 17, the end-flanges 21 successively engage the ends of the plies, the longest or outer ply first and the shortest or inner ply last, as the ply-portions which are being bent slide on each other from their initial flat position shown in Fig. 1 through their intermediate position shown in Fig. 2 to their fully bent position shown in Fig. 3. In this fully bent position, the bent portions of each ply lie tight against its neighbor or neighbors, between the forming blocks 16 on the inside of the bends and the metal of the flexible forms 15 on the outside of the bends; and the end flanges 21 bear tightly against 'the ends of all the plies and by their reaction 'is removed from the bending machine and the wood on it'is suitably dried; and another form 15 is put on the bending machine for the next load. When the wood on a form is set it may be removed from the form 15, as is shown in Fig. 5, and if more drying is to be done it may be done in any usual manner.

When the wood is fully dried, which may require several days, the plies of. a group are separated, as shown in Fig. 6, and glue is applied to the various abutting surfacesthereof. Then the group of plies is promptly reassembled in the same order as during bending, and desirably in the same relative positions although in suitably symmetrical articles it is not unduly harmful if one or more of the plies are turned end for end with relation to the other plies. Then the group of plies is put on a gluing form 30, on which the reassembling itself may be done, and'the plies pressed firmly together and the inner ply pressed against the gluing form by any suitable clamping means; as shown b simple carpenters clamps 31 which each ave one jaw in a hole 32 in thegluing form 30 and the other pressing against the outer ply 13, with or without any interposed block 34.

When the glue has set, the built-up gluedtogether structure is removed from the gluing form, and worked and finished to the desired shape, such for instance as that shown in the left-hand part of Fig. 8. The finished article may be made to definite dimensions, and with rare exceptions retains the desired final shape and dimensions indefinitely with very little variation and none beyond commercial limits.

I claim as my invention:

1. The process of making a bent-wood-article, comprising bending a plurality of steamed relatively thick superposed plies of lumber so that each ply serves as a form for its neighbor or neighbors, then letting the assembled group of plies dry and set while they are held together, and then gluing said plies together in the same relative order they had during the bending.

2. The process of making a bent-wood article, comprising bending a plurality of steamed superposed plies of lumber so that each ply serves as a form for its neighbor or neighbors, then letting the assembled group of plies dry and set while they are held .to gether, and then gluing said plies together in the same relative order they had during the bending.

3. The process of making a bent-wood article, comprising bending simultaneously a plurality of steamed superposed plies of lumber so that each ply serves as a form for its 5 neighbor or neighbors, then letting the'assembled group of plies dry and set while they are held together, and then gluing said plies together in the same relative order they had during the bending.

4. The process of making a bent-wood article, comprising bending a plurality of steamed relatively thick superposed plies of lumber so that each ply serves as a form for its neighbor or neighbors, then letting the assembled group of plies dry and set while they are held together, and then gluing saidplies together in the same relative order and positions they had during the bending.

5. The process of making a bent-wood article, comprising bending a plurality of steamed superposed plies of lumber so that each ply serves as a form for its neighbor or neighbors, then letting the assembled group of plies dry and set while they are held together, and then gluing said. plies together in the same relative order and positions they had during the bending.

v 6. o The process ofmaking a bent-wood article, comprising bending. simultaneously a plurality of steamed superposed plies of lumber so that each ply serves as a form for its neighbor or neighbors, then letting the assembled group of plies dry and set while they are held together, and then gluing said plies together in the same relative order and positions they had during the bending. 5

7. A bent wood article, comprising a plurality of superposed plies of relatively thick wood that had been bent and dried together,

a form for its neighbor or neighbors, and

then glued together with the plies in the same gelatiive order .in which they were bent and 9. A bent wood article, comprising a plurality of superposed plies of relatively thick wood that had been bent and dried together, with each ply serving as a form for its neighbor or neighbors, and then glued together with the plies'in the same relative order and positions in which they were'bent "and dried.

10. A bent wood article, comprising a plurality of superposed plies that had been bent and dried together, with each ply serving as a form for its neighbor or neighbors, and then glued together with the plies in the same relative order and position in which they were bent and dried.

11. The process of making; a bent-wood article, comprising bending a plurality of superposed plies of lumber so thateach ply serves as a form for its neighbor or neighbors, then letting theassembled group of plies set while held together, and then gluing the plies together in the same relative order they had during the bending.

In witness whereof, I have hereunto set my hand at Delphos, Ohio, this 29th day of October, A. D. one thousand nine hundred and 

